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PubMed2003

Poor correlation of mid-femoral measurements by CT and hip measurements by DXA in the elderly.

BACKGROUND AND AIMS: Hip fracture is a devastating event in terms of outcome in the elderly, and the best predictor of hip fracture risk is hip bone density, usually measured by dual X-ray absorptiometry (DXA). However, bone density can also be ascertained from computerized tomography (CT) scans, and mid-thigh scans are frequently employed to assess the muscle and fat composition of the lower limb. Therefore, we examined if it was possible to predict hip bone density using mid-femoral bone density. METHODS: Subjects were 803 ambulatory white and black women and men, aged 70-79 years, participating in the Health, Aging and Body Composition (Health ABC) Study. Bone mineral content (BMC, g) and volumetric bone mineral density (vBMD, mg/cm3) of the mid-femur were obtained by CT, whereas BMC and areal bone mineral density (aBMD, g/cm2) of the hip (femoral neck and trochanter) were derived from DXA. RESULTS: In regression analyses stratified by race and sex, the coefficient of determination was low with mid-femoral BMC, explaining 6-27% of the variance in hip BMC, with a standard error of estimate (SEE) ranging from 16 to 22% of the mean. For mid-femur vBMD, the variance explained in hip aBMD was 2-17% with a SEE ranging from 15 to 18%. Adjusting aBMD to approximate volumetric density did not improve the relationships. In addition, the utility of fracture prediction was examined. Forty-eight subjects had one or more fractures (various sites) during a mean follow-up of 4.07 years. In logistic regression analysis, there was no association between mid-femoral vBMD and fracture (all fractures), whereas a 1 SD increase in hip BMD was associated with reduced odds for fracture of approximately approximately 60%. CONCLUSIONS: These results do not support the use of CT-derived mid-femoral vBMD or BMC to predict DXA-measured hip bone mineral status, irrespective of race or sex in older adults. Further, in contrast to femoral neck and trochanter BMD, mid-femur vBMD was not able to predict fracture (all fractures).

Absorptiometry, Photon↗
PubMed2003

Definition of a population-specific DXA reference standard in Italian women: the Densitometric Italian Normative Study (DINS).

Osteoporosis is currently defined on the basis of the T-score by dual-energy X-ray absorptiometry (DXA). Despite its limitations, this definition is applied worldwide. However, the normal values provided by manufacturers may not be fully representative of specific local populations. So far, there are no normative data in the Italian population using Hologic densitometers. The Densitometric Italian Normative Study (DINS) is an ongoing multi-center study that aims to establish reference values for bone densitometry with dual-energy X-ray absorptiometry (DXA) in the male and female Italian population. In this paper we report the results of the lumbar vertebrae (L2-L4) and proximal femur in 1,622 women aged 20-79 years. Bone mineral density (BMD) was determined using dual-energy X-ray absorptiometry (DXA) on Hologic bone densitometers (Hologic, Waltham, Mass.). Most of the subjects were examined with a QDR 4500. The BMD of the lumbar vertebrae was virtually constant between 20 and 49 years (test for trend: P=0.66); the BMD values between 20-45 in premenopausal women (mean 1.036; SD 0.109 g/cm(2)) were thus defined as the peak bone mass values, significantly lower compared to the Hologic reference curve (mean 1.079, SD 0.11 g/cm(2)). The mean BMD values of the femoral neck were virtually identical to those of the NHANES study in the first 3 decades; after the age of 50 the BMD values were slightly greater than those of the NHANES subject. The subject classification according to the WHO criteria was similar using the DINS and NHANES reference values for the femur; for the spine, the Hologic reference values classified a larger proportion of women as osteoporotic (21 vs. 16%) or osteopenic (42 vs. 38%) compared to DINS.

Absorptiometry, Photon↗
PubMed1999

An unexpected change in DXA calibration not detected by routine quality control checks.

Since its commercial introduction a decade ago, the technique of dual-energy X-ray absorptiometry (DXA) has been widely recognized as a useful and sensitive method of measuring changes in bone mineral density (BMD) at selected sites in the skeleton such as the spine and proximal femur. Because of their high precision and stable calibration, DXA scanners are frequently used in clinical trials to evaluate new treatments for osteoporosis. Quality assurance procedures based on regular scanning of phantoms are widely adopted in such trials, and continuity of the phantom BMD measurements is generally believed to ensure continuity in the in-vivo calibration. We report a change in calibration of a DXA scanner that occurred during a clinical trial where the calibration shift was different for the spine and femur sites and was not predicted or explained by the standard quality control procedures using phantoms. However, we show that provided patients enrolled in studies are thoroughly randomized and the statistical analysis is confined to the differences between the treated and control groups, then the effects of such calibration shifts on conclusions regarding the efficacy of treatment are considerably smaller than the random statistical errors.

Absorptiometry, Photon↗
PubMed2001

DXA of the hip and heel ultrasound but not densitometry of the fingers can discriminate female hip fracture patients from controls: a comparison between four different methods.

Dual-energy X-ray absorptiometry (DXA) of the proximal femur and in more recent years quantitative ultrasound (QUS) of the heel are the most established methods for assessing hip fracture risk. Measurement of the fingers offers a new approach. We performed DXA of the proximal femur, QUS of the heel and fingers, and radiographic absorptiometry (RA) of the fingers in 87 non-institutionalized women, 65-85 years of age, with a first hip fracture and compared them with 195 randomly selected age-matched controls. Bone mineral density (BMD) of the femoral neck and heel Stiffness Index were significantly lower among cases than among controls (by 15% and 17%, respectively; p < 0.0001), whereas no significant differences were found for finger measurements. When applying the WHO criterion of osteoporosis, 62-98% of the patients were classified as osteoporotic, compared with 19-85% of the controls, depending on method and site. The risks of hip fracture, estimated as odds ratios for every 1 SD reduction in femoral neck BMD, heel Stiffness Index, finger QUS and finger RA, were: 3.6 (95% CI 2.4-5.5), 3.4 (95% CI 2.2-5.0), 1.0 (95% CI 0.7-1.3) and 1.2 (95% CI 0.8-1.6), respectively. Compared with women with normal BMD of the femoral neck, those classified as osteopenic had an odds ratio of hip fracture of 14 (95% CI 2-110), whereas those classified as osteoporotic had an odds ratio of 63 (95% CI 8-501). We conclude that hip DXA and heel QUS have similar capacities to discriminate the risk of a first hip fracture, whereas QUS and RA of the phalanges seem inferior techniques for differentiating female hip fracture patients from controls.

Absorptiometry, Photon↗
PubMed1998

The effect of trabecular structure on DXA-based predictions of bovine bone failure.

The objective of this study was to determine the influence of structural organization on the relationship between clinically assessed bone mineral density (BMD) and strength of trabecular bone. Accurate assessment of bone strength or fracture risk is a critical need as the population ages and the incidence of fractures increases. While ex vivo tests have demonstrated that BMD measured with dual-energy X-ray absorptiometry (DXA) correlates with failure load of whole bones, it is also known that the strength of trabecular bone cannot be explained by density alone. Cylindrical cores of bovine trabecular bone, harvested in a variety of orientations, were scanned with DXA to determine density, assessed with micro-MRI (magnetic resonance imaging) to measure orientation, and then loaded them to failure in bending. Measures of trabecular architecture included the angle between the specimen longitudinal (Z) axis and the principal material axis, the maximum mean intercept length (MILmax), the mean intercept length in the specimen primary axis (MILz), the degree of anisotropy, and the ratio between MILz and the length of the principal material axis. MILz was strongly associated with failure stress (r2 = 0.85, P < 0.001). BMD was also moderately associated with failure stress (r2 = 0.44, P = 0.004). Using a stepwise linear multiple regression analysis, the strongest predictor of failure stress was a combination of BMD, angle, and MILz (R2 = 0.91). When only longitudinal specimens were analyzed, the strongest predictor of failure stress was a combination of BMD and angle (R2 = 0.95). Therefore, trabecular orientation plays a significant and important role in failure of trabecular bone. Accounting for this may improve the associations between DXA-based density measures and patient fractures.

Absorptiometry, Photon↗
PubMed2005

Bone mineral content, corrected for height or bone area, measured by DXA is not reduced in children with chronic renal disease or in hypoparathyroidism.

The combination of poor growth and parathyroid and mineral disorders complicates the diagnosis of renal bone disease in children with chronic renal insufficiency (CRI), and the role of dual X-ray absorptiometry (DXA) is unclear. We aimed to examine the role of DXA in assessing variation in size-adjusted bone mineral content (BMC) in children with CRI and compare it with a cohort with hypoparathyroidism (HPT) and pseudo-hypoparathyroidism (PHPIa). In 29 patients with CRI (21 male) with a median age of 11 years (10th, 90th centiles 4.4, 14.6) and 10 patients with HPT and PHPIa (three male), with a median age of 13.7 years (7, 16) lumbar spine (LS) and total body (TB) BMC were measured by DXA. Age-, gender- and height-matched data allowed calculation of percentage predicted bone area for age and gender (pBAr) and percentage predicted BMC for bone area and height. In the CRI group, the median glomerular filtration rate (GFR) was 27.4 ml/min per 1.73 m2 (7.1, 69.5), and the median duration of illness was 9.3 years (2.1, 12.1). Median height standard deviation score (Ht SDS) was -1.6 (-3.0, 0.3), and, as expected, median LS and TB pBAr were low at 82% (68, 974) and 76% (63, 92), respectively. LS and TB predicted BMC (pBMC) SDS (corrected for bone size) were generally high, with a median value of 0.4 (-0.9, 1.4) and 0.4 (-0.1,0.9), respectively. Analysis of the prepubertal subset of children (n=15) showed that median percentage predicted LS BMC for height was 104% (80, 116), whereas the median TB BMC for height was 96% (74, 108). Median Ht SDS of the HPT and PHPIa cohort was -0.3 (-2.9, 0.3) and median LS and TB pBAr were 90% (66, 100) and 91% (76, 98), respectively. Median LS and TB pBMC SDS were 0.6 (-0.4, 1.8) and 0.7 (0.3, 1.1), respectively. Median percentage predicted LS and TB BMC for height were 102% (82, 114) and 102% (92, 122). There was no relationship between pBMC SDS and duration of illness, GFR, vitamin D dose, serum intact parathyroid hormone (PTH), serum calcium/phosphate product or serum total alkaline phosphatase (ALP) in the CRI or the HPT cohort. However, one of the highest pBMC SDSs was recorded in a child with PHPIa before she started on any treatment. In children with CRI, BMC, when adjusted for co-existing growth retardation, is similar to that observed in children with hypoparathyroidism. The correct reading of BMC needs a correction for bone size.

Absorptiometry, Photon↗
PubMed2003

DXA vs QCT for subclinical celiac disease patients.

It has been recognized that celiac disease (CD) may be associated with osteoporosis. However, few data exist regarding bone disorders in adult patients with subclinical CD (SCD) and the best densitometric technique for assessing bone mineral density (BMD). We compared dual X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) in measuring the lumbar spine of 23 female patients with SCD and 19 healthy subjects. There were lower densitometric values in the subjects with SCD than the control group. We found discordance between DXA and QCT results using World Health Organization (WHO) criteria with the T score. With QCT as the reference method for its sensitivity, we found one false-negative, two false-positive and two misdiagnosed cases. We suggest some correction factors to improve DXA evaluation and screening of bone loss in CD.

Absorptiometry, Photon↗
PubMed1995

The European Spine Phantom--a tool for standardization and quality control in spinal bone mineral measurements by DXA and QCT.

The lack of standardization in bone mineral measurements of the lumbar spine and other skeletal sites is generally recognized as an important and unresolved issue. We report and discuss efforts at standardization and cross-calibration of DXA and QCT equipment. We have designed and tested a geometrically defined, semi-anthropomorphic phantom, the European Spine Phantom (ESP). It contains a spine insert consisting of three vertebrae of increasing bone mineral densities and thicknesses of cortical structures; the respective parameters are given in tabular form for the final phantom design. Results for cross-calibration with the ESP compare well with patient results. Measurements on the first 30 phantoms confirmed that the ESP can be manufactured with a variation of about 1%. We conclude that the ESP is suitable for daily quality assurance, cross-calibration of instruments and universal standardization. The ESP was used to establish standardized BMD (sBMD) units for DXA equipment going into effect in late 1995. Its acceptance by manufacturers as a calibration standard for DXA and QCT measurements appears imminent.

Absorptiometry, Photon↗
PubMed1992

Measurements of bone mineral density by DXA total body absorptiometry in different skeletal sites in postmenopausal osteoporosis.

In order to evaluate the bone mineral density (BMD) of the entire skeleton and its major anatomical areas, total body DXA absorptiometry was performed in 330 postmenopausal women whose ages ranged from 42-85 years. Sixty-three of them were normal women and constituted the control group (Group 1). Two hundred sixty-seven were patients affected with postmenopausal osteoporosis: 107 osteoporotic patients had vertebral biconcavity deformities of grade 1 (Group 2), and the other 160 had vertebral wedge, biconcavity, and compression deformities of grade 2 (Group 3). Total body absorptiometry was assessed by a DXA system (Lunar DPX). Significant reduction in total body BMD values was observed in patients in Groups 2 and 3 (p less than 0.01): the bone loss was more intense in osteoporotic women of Group 3. The low values of the BMD in osteoporotic patients are, moreover, localized in the areas of spine, arms, and legs; the osteopenia was particularly enhanced in patients with grade 2 vertebral deformities. Multiple linear regression indicated that values of total BMD were significantly related to age and BMI. Receiver operating characteristic (ROC) analysis showed that total BMD provided high sensitivity: At 90% of specificity it was 78% for Group 2 and 89% for Group 3. DXA total body absorptiometry has demonstrated that, in postmenopausal osteoporotic women, the reduction in bone mass is not localized only in the spine, but also involves the appendicular skeleton.

Absorptiometry, Photon↗
PubMed2005

Dual energy X-ray absorptiometry (DXA): can it detect acute scaphoid fractures?

This prospective study investigated whether dual energy X-ray absorptiometry (DXA) could detect acute scaphoid fractures. We blindly compared 10 normal and 10 fractured scaphoid images produced with a new technique of DXA scan analysis. This measured and plotted the density of the scaphoid throughout its length, producing a linear graph of the scaphoids' density instead of a single area (g/cm2) measurement of bone density. These new plots only detected six of the 10 fractures and suggested that four of the normal controls were fractured. Thus, this technique of DXA scan analysis is neither sensitive nor specific for the detection of acute scaphoid fractures.

Absorptiometry, Photon↗
PubMed2006

Derivation of whole body bone measures through summation of individual DXA scans.

A major limitation of dual-energy X-ray absorptiometry (DXA) instruments is the size of the scanning region that precludes obtaining accurate data on individuals who are very wide and/or tall. The purpose of this study was to determine if whole body bone mineral values can be determined in individuals too wide and/or too tall for the scanning region using summed measures from multiple DXA scans. Two to four partial scans of the body were combined to predict bone mineral content (BMC) and bone mineral density (BMD) from a complete whole body (WB) scan. The results indicate that compared with the WB scan, there were strong relations and small differences when summing scans to simulate a wide or tall individual for BMC (wide: r = 0.999, mean [M] +/- standard deviation(diff) [SD](diff) = -2.1 +/- 26.2 g, p = 0.62; tall: r = 0.999; M +/- SD(diff) = -5.9 +/- 27.1 g, p = 0.17) or BMD (wide: r = 0.996; M +/- SD(diff) = 0.001 +/- 0.011 g/cm(2), p = 0.54; tall: r = 0.994; M +/- SD(diff) = 0.004 +/- 0.014 g/cm(2), p = 0.10). Notably the differences from the whole body scan were within measurement error. In conclusion, accurate assessment of bone mineral outcomes can be obtained on wide or tall individuals using summed values from multiple DXA scans.

Absorptiometry, Photon↗
PubMed2006

Effect of calcium tablets on interpretation of lumbar spine DXA scans.

Undissolved calcium (Ca) tablets in the gastrointestinal tract at the time of a dual-energy X-ray absorptiometry (DXA) scan could conceivably affect the accuracy of the lumbar spine bone mineral density (BMD) determination. We studied phantoms and volunteers to determine the effect of Ca tablets overlying bone, Ca tablets in the soft-tissue field, and Ca tablets overlapping both bone and soft tissue. For L1-4, a 500-mg Ca tablet taped to the phantom surface or the skin of volunteers resulted in <or=2.2% mean increase in measured BMD (less than the lumbar spine least significant change), changing the T-score for L1-4 very little. However, an overlying Ca tablet had a substantial effect on BMD of a single vertebral body. Greater effects were seen with higher amounts of tablet Ca and with lower BMD, resulting in as much as a 12.6% mean increase in single vertebral BMD in the in vivo series. Recent versions of DXA software successfully identified tablets in the soft-tissue field as artifact and eliminated the tablet pixels from the analysis. However, tablets overlapping bone and soft tissue necessitated operator intervention to either exclude the affected vertebral body or adjust edges by mapping the tablet as artifact and/or neutral field. A paraffin-coated Ca tablet swallowed by a volunteer was tracked serially by DXA during gastrointestinal transit. Similar effects were seen as with the phantom and volunteer studies using external tablets; there was little effect of the Ca tablet on L1-4 BMD either with the tablet overlying bone or in the soft-tissue field. We conclude that undissolved Ca tablets introduce small artifacts on L1-L4 BMD insufficient to alter diagnostic categorization of patients. However, if only two or three vertebral levels are available, misclassification of the patients may occur due to tablet artifact. The precision of monitoring BMD over time could also be adversely affected by tablet artifact if a tablet was directly overlying bone and undetected, especially with smaller regions of interest and with lower baseline BMD.

Absorptiometry, Photon↗
PubMed2006

Measurement error of DXA: interpretation of fat and lean mass changes in obese and non-obese children.

Information on reproducibility of dual-energy X-ray absorptiometry (DXA) measurements is essential because DXA is frequently used by clinicians and researchers to assess body composition changes. We estimated measurement error and absolute and relative smallest detectable differences (SDDs) for fat, lean, and bone mass in children. The SDD is the change necessary to be confident that the change is not a consequence of measurement error. Duplicate whole body DXA (Hologic QDR 4500A, Hologic Inc., Waltham, MA) scans were obtained on 32 obese and 34 non-obese children ages 6-19 yr. Absolute (kg) and relative (coefficient of variation) measurement error and SDD were calculated. Absolute SDDs for fat and lean were higher for obese (1.39 and 1.30 kg, respectively) than for non-obese children (0.42 and 0.47 kg, respectively). The %SDD for fat was lower for obese (3.58%) than non-obese children (5.24%), but for lean the %SDD was higher for obese (2.60%) than non-obese children (1.32%). The SDDs for bone mass were similar for obese and non-obese children. An obese child must lose or gain more absolute fat and lean mass than a non-obese child to be confident that the change is not a reflection of measurement error. Overall, SDD values for fat, lean, and bone mass are low.

Absorptiometry, Photon↗
PubMedDate not supplied

Simulated change in body fatness affects Hologic QDR 4500A whole body and central DXA bone measures.

Changes in body fatness may impact the accuracy of dual energy X-ray absorptiometry (DXA) measures of bone mineral content (BMC) and bone mineral density (BMD). The aim of this study was to determine if DXA can accurately assess BMC and BMD with changes in exogenous fat (lard) placed to simulate weight change. Whole body (WB), lumbar spine (LS), and proximal femur (PF) DXA scans (Hologic QDR 4500A) were performed on 30 elderly (52-83 yr) and 60 young (18-40 yr) individuals (i.e., 45 females and 45 males) of varying body mass index (mean+/-standard deviation: 26.1+/-4.9 kg/m2). When scans were repeated with lard packets (2.54 cm thick, 25.4x17.8 cm, 1 kg), WB BMD decreased 1.1% and 1.6% after chest and thigh packet placement, respectively (p=0.001), PF BMD increased 0.7% (p=0.02) and LS BMD decreased 1.6% (p=0.001) primarily due to a 2.2% reduction in LS BMC (p<0.001). Initial LS BMC and trunk mass were related to error in LS BMC measures due to lard-loading (r=0.64 and 0.45, respectively, p<0.001). We conclude that on average simulated weight change minimally impacts PF bone measures and moderately impacts WB and LS bone measures; however, individual variability in measurement error was noteworthy and may be impacted by body thickness.

Absorptiometry, Photon↗
PubMed1999

[Sex-specific analysis of bone mass in normal and growth hormone transgenic mice using dual energy x-ray absorptiometry (DXA)].

The aim of the present study was the non-invasive, sex-specific measurement of bone mass in bovine growth hormone (bGH) transgenic mice and normal controls with dual energy X-ray absorptiometry (DXA). The transgenic mouse constitutes a suitable animal model to study the influence of growth hormone on the skeletal system. We analysed 28 animals, aged 12 weeks (14 transgenic, 14 controls, 7 male and 7 female, respectively), using a peripheral DXA scanner that had been adapted to the measurement of small animals. At a measurement time of 20 min, the precision (RMS average CV%) was 4.4% for bone mass (BMC), 2.5% for areal bone density (BMD), 0.86% for total body weight and 4.5% for the percentage BMC (relative to body weight). While the absolute bone mass was not significantly different between male and female animals, we found a higher percentage of the BMC relative to the total bone mass in females (+21% in controls, +31% in transgenics; p < 0.01). The absolute bone mass was higher in the transgenic animals (+71% in females and +62% in males; p < 0.01), but relative to the body weight the transgenic females yielded similar and the transgenic males lower values (-7.2%; p < 0.05). Using DXA it is possible to non-invasively determine the mass of mineralised tissue in the mouse with relatively high precision and to effectively discriminate between different groups. Although a strong influence of growth hormone on the absolute bone mass is observed, the results show that this increase is not higher than that of the total body mass.

Absorptiometry, Photon↗
PubMed2001

Comparison of two software versions for assessment of body-composition analysis by DXA.

OBJECTIVE: To compare two software versions provided by Lunar CO: for assessment of body composition analysis by DXA. RESEARCH METHODS AND PROCEDURES: Soft-tissue phantoms for lean tissue (water) and fat tissue (methanol) were repeatedly scanned using DXA machines (DPX-L; Lunar CO., Madison, WI) and analyzed using software version 1.33 and the updated year 2000-compatible version 1.35. For the intersoftware comparison, the phantoms were scanned 10 times (each scan was analyzed once) with both software versions using all three scanning modes (slow, medium, and fast) for a total of 60 scans and analyses. For the intermachine comparison, the same phantoms were scanned three times (each scan was analyzed once) with a second machine from the same manufacturer using all three scanning modes and version 1.35 only. Percentage of fat was the variable of interest. RESULTS: For version 1.33, fat was 9.9 +/- 0.4%, 10.0 +/- 0.5%, and 11.0 +/- 0.5% (mean +/- SD) for the lean-tissue phantom and 50.8 +/- 0.3%, 50.9 +/- 0.5%, and 51.1 +/- 0.6% for the fat-tissue phantom using the slow, medium, and fast scanning modes, respectively. For version 1.35, the respective fat values were 9.8 +/- 0.7%, 9.9 +/- 0.4%, and 10.3 +/- 0.7%, and 50.6 +/- 0.5%, 50.9 +/- 0.6%, and 50.8 +/- 0.8%, respectively. For the lean-tissue phantom, the estimation of percentage of fat was significantly (p < 0.05) affected by scanning mode but not by software version. For the fat-tissue phantom, the estimation of percentage of fat was not affected by either scanning mode or software version. The use of version 1.35 did not effect intermachine variability. DISCUSSION: Versions 1.33 and 1.35 of the Lunar body composition software appear to be comparable. Soft-tissue phantoms, such as the ones described in this paper, may be useful in monitoring the reproducibility of body composition analyses within and between DXA machines, particularly in longitudinal studies.

Absorptiometry, Photon↗
PubMed2002

Fat mass measured by DXA varies with scan velocity.

OBJECTIVE: To study the influence of scan velocities of DXA on the measured size of fat mass, lean body mass, bone mineral content and density, and total body weight. RESEARCH METHODS AND PROCEDURES: The subjects were 71 healthy white adults, 38 women and 33 men. The mean age was 41.7 +/- 13.5 years and body mass index was 28.6 +/- 5.6 kg/m(2). The subjects were scanned consecutively in slow, medium, and fast scan mode by a Lunar DPX-IQ DXA scanner. RESULTS: Throughout the body mass index and sagittal height ranges, scanned lean body mass significantly decreased with higher scan velocity and lean body mass was 2.7% lower in fast than in medium mode (p < 0.0001). In contrast, fat mass, percentage of body fat, and bone mineral contents were higher with increasing scan velocity. Areas not analyzed by the scanner, so called blue spots, increased with scan velocity and sagittal height, and their presence significantly enhanced the error. Body weight estimated by DXA in slow mode was -0.8% lower than scale weight in the women (p < 0.001) and -0.2% in men (not significant), and the difference was greater with increasing scan velocity. DISCUSSION: Scan velocity significantly influences the measured fat mass size, lean body mass, bone mineral content, and body weight. To obtain the most accurate results, slow mode is preferable and fast scans should be avoided. Future studies should report and take scan velocity into consideration.

Absorptiometry, Photon↗
PubMed2002

DXA: potential for creating a metabolic map of organ-tissue resting energy expenditure components.

OBJECTIVE: This study tested the hypothesis that tissue-organ components can be derived from DXA measurements, and in turn, resting energy expenditure (REE) can be calculated from the summed heat productions of DXA-estimated brain, skeletal muscle mass (SM), adipose tissue, bone, and residual mass (RM). RESEARCH METHODS AND PROCEDURES: Subjects were divided into five groups of adults <50 years of age. The specific metabolic rate of RM was developed in 13 Group I healthy subjects and a DXA-brain mass prediction formula in 52 Group II subjects. SM, adipose tissue, and bone models were developed based on earlier reports. The composite REE prediction model (REEp) was tested in 154 Group III subjects in whom REEp was compared with measured REE (REEm). Features of the developed model were determined in 94 normal-weight men and women (Group IV) and seven spinal cord injury patients and healthy matched controls (Group V). RESULTS: REEp and REEm in Group III were highly correlated (y = 0.85x + 233; r = 0.82, p < 0.001), and no bias was detected. Both REEm (mean +/- SD, 1,579 +/- 324 kcal/d) and REEp (1,585 +/- 316 kcal/d) were also highly correlated (r values = 0.85 to 0.98; p values < 0.001) and provided similar group values to REE estimated by the Harris-Benedict equations (1,597 +/- 279 kcal/d) and Wang's composite fat-free mass-based REE equation (1,547 +/- 248 kcal/d). New insights into the sources and distribution of REE were provided by analysis of the demonstration groups. DISCUSSION: This approach offers a new practical and educational opportunity to examine REE in subject groups using modeling strategies that reveal the magnitude and distribution of fundamental somatic heat-producing units.

Absorptiometry, Photon↗